Sea lions in Southern California waters had rarely posed a problem for beachgoers, surfers and swimmers, until now.
Scientists say a naturally occurring bloom of toxic algae, a neurotoxin, is infecting local populations of sea lions and other marine mammals, making them lethargic, giving them seizures and, in some cases, making them aggressive.
Over the weekend, a 15-year-old girl endured a terrifying attack by an aggressive sea lion during her swim test for the cadet lifeguard program in Long Beach, leaving her with bites, scratches and bruises on her arm.
A week earlier, a surfer in Oxnard reported a sea lion attack as well.
Officials at the Marine Mammal Care Center in San Pedro say that from Malibu to Long Beach, they are seeing a record number of sick sea lions and dolphins stranded along the Los Angeles’ coastline.
“We have seen over 250 animals this year so far, when, normally, over an entire year we only see 300,” MMCC Marine Biologist Dave Bader told KTLA’s Angeli Kakade.
Bader told KTLA that the intensity of the bloom off Southern California waters is the result of climate change.
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Phoebe Beltran, 15, was attacked an aggressive sea lion during a test swim for life guard cadets in Long Beach on March 30, 2025. (Bibi Beltran) -
Phoebe Beltran, 15, was attacked an aggressive sea lion during a test swim for life guard cadets in Long Beach on March 30, 2025. (Bibi Beltran) -
Phoebe Beltran, 15, was attacked an aggressive sea lion during a test swim for life guard cadets in Long Beach on March 30, 2025. (Bibi Beltran) -
Sick sea lions at the Marine Mammal Care Center in San Pedro. (KTLA) -
Marine Mammal Care Center employee bringing in another sick sea lion on April 1, 2025. (KTLA) -
Marine Mammal Care Center employee bringing in another sick sea lion on April 1, 2025. (KTLA) -
Sick sea lions at the Marine Mammal Care Center in San Pedro. (KTLA) -
A dolphin likely sickened by a toxic algal bloom seen stranded on a SoCal beach. (KTLA)
“This is not normal,” he said. So, not normal behavior is one of the things that would make us say, ‘This animal has probably got a neurotoxin.’”
The danger to people encountering sick and aggressive sea lions can be serious. The marine mammals can weigh as much as 700 pounds and span six feet.
In the case of the teenage girl, lifeguards watching the swim test rushed out to help get her back to shore, where she was then taken to the hospital for treatment of her injuries. Fortunately, she wasn’t seriously injured, though she’s out of the water for now.
The surfer was able to make his way back safely back to land as well.
“I would say that if you see a sea lion in and around an area you’re swimming in, you should probably come out of the water and give that animal space,” Bader said.
The biologist added that, at least for now, the toxic algae blooms show no signs of slowing down and people should use caution when going into the ocean.
Anyone who encounters a sick or stranded marine mammal can alert the nearest lifeguard and call 1-800-39-WHALE to make a report.
